Lower unit for outboard motors



NOV. 19, 1935. F, T |RGEN$ 2,021,309

LOWER UNIT FOR OUTBOARD MOTORS Filed Feb. l0, 1933 2 Sheets-Sheet 1 INVENTOR #mmv www mw ATTORN EYS Nouv. 19, 1935. F, T` lRGENs 2,021,309

LOWER UNIT FOR OUTBOARD MOTORS Filed Fe b. l0, 1933 2 Sheets-Sheet 2 INVENTOR SAAMX wma. j

ATTORNEYS Patented Nov. 19, 1935 PATENT OFFICE 2,021,399 LOWER UNIT Fon. oU'rBoARD Mo'rons Finn T. Irgens, Wauwatosa, Wis., assignor to Outboard Motors Corporation, Milwaukee, Wis., a corporationV of Michigan Application February 10, 1933, Serial No. 656,089

12 Claims.

This invention relates to improvements in lower units for outboard motors.

One of the objects of the invention is to provide a lower unit which may be of stream-lined contour in horizontal cross section but which will, nevertheless, deviate from the -customary smooth walled housing by the provision of a series of longitudinally extending ribs or flutes which will have the effect of interlocking or interconnecting the lower unit of the outboard motor structure to the Water through which such unit is passing, whereby the mass of the water will resist tendency to vertical vibration of the parts.

I am aware of the fact that it has been proposed heretofore to employ a widely extending flange or plate for this purpose. Such a plate, however, offers a very substantial increase in water resistance and will be found to be less eiective than the flutes herein disclosed, which not only perform the above mentioned function, but also strengthen the lower unit to such an extent that it is possible to decrease its weight without sacrificing its strength.

In the various exemplications of the invention herein disclosed, there are other features which satisfy objectives of the present invention. As to one of these features it is an object to providea connecting structure for a lower unit which is so designed as to make it unnecessary to extend the stream-lining of the lower unit above the anti-cavitation plate. It is also a purpose of the invention to discharge exhaust gases in the plane of the anti-cavitation plate without discharging them through the plate.

It is a further object of the invention to provide a novel and improved lower unit in which the expense of casting the unit is very substantially reduced by manufacturing the anti-cavitation plate separately and so attaching it to the unit that it will appear as if made integral therewith and will not present any joints so disposed as to catch weeds. More .specifically stated, it is my purpose to provide an anti-cavitation plate lwhich is bifurcated to` receive the lower unit,

preferably being slipped thereon from the front. 'I'he lower iuiit may be slotted for interlocking engagement with'the anti-cavitation plate, and an exhaust outlet may be employed as a means for boltingv the anti-cavitation plate ln plae about the lower unit.'

It is a further object of the invention to provide an outboard motor lower unit in which the propeller hub is locatedclosely adjacent the bevel gearing which connects the drive shaft with the propeller shaft. By means of this disposition of the hub I am enabled, in a generally stream-lined lower unit; to avoid the awkward and bulky torpedo'- or barrel-shaped gear chamber which has so commonly been employed in devices of this kind. Such a gear chamber has assumed the barrel form because of the supposed necessity of carrying the maximum diameter of the gear casing rearwardly to meet the propeller hub. By moving the propeller hub forwardly adjacent the pointat which the casing reaches its maximum diameter, the barrel shape is wholly eliminated and the propeller becomes practically weedless due to the iluted form of the gear casing and the extremely close proximity of its rear margin to `the path ef travel ef the propeller blades.

In the drawings:

Figure 1 shows partially in side elevation and partially in vertical axial section, an embodiment of the invention.

Figure 2 is a detail view taken in section in 25 y the plane indicated at4 2-2 in Figure 1.

Figure 3 is a detail in plan of the upper'face of the lower unit, the anti-cavitation plate structure having been removed to the plane indicated at a-a in Figure 1.

Figure 4 is adetail view taken in section in the plane indicated at 4-4 in Figure 1.

Figure 5 is a view in side elevation of a modied embodiment of the invention, a portion of its wall being broken away to expose the inlet water passage.

Figure 6 is a detail` View of the construction shown in Figure 5, taken in cross section inthe plane indicated at 6-6 in Figure 5. 40

Figure 7 is a detail view in perspective showing the manner in which the exhaust manifold and anti-cavitation plater are attached to each other about the lower unit.

Figure 8 is a side elevation of a further modi- 45 ed embodiment of the invention.

Figure 9 is a detail view taken in section in the plane indicated at 9-9 in Figure 8.

Figure 10 is a fragmentary rear elevation of 50 the device shown in Figure 8.

Like parts are identified by the same reference characters throughout the several views.

The lower unit of an outboard motor is an lntegral casting which conventionally includes a gear casing, bevel gears therein connecting the vertical drive shaft with the propeller shaft, and bearings for said shafts. is usually a torpedoshaped enlargement of the lower unit as a whole, the lower unit including a streamlined upward extension joined to a shaft housing by which the lower unit is carried from the remainder of the outboard motor structure.

In the construction shown in Figs. 1 to 4, the lower unit is designated generically by reference character I5. It includes the conventional torpedo-shaped gear chamber I6, skeg I1, and stream-lined upward extension I8 which terminates in a generally planiform surface I9 recessed at to provide a pump chamber as shown in Fig. 3. The vertical drive shaft 2l carries a centrifugal pump runner 22 to which water may conveniently be supplied by a duct 23 formed within the terminal flange 2l of shaft housing 25. Said flange is preferably made sufficiently wide to serve as an anti-cavitation plate. Bolts 26 extend through it to connect the shaft housing with the lower unit at a point below the water line.

The anti-cavitation plate flange 24 terminates at 28 slightly in advance of the rear margin 29 of the lower unit. Its rear portion is recessed at 30 to receive an under-water exhaust fitting 35 which is bolted at 36 to the anti-cavitation plate or flange 2Q and has a relatively flat broad discharge mouth il@ opening rearwardly substantially in the plane of the anti-cavitation plate, whereby to take advantage of the aspirating effect produced by the water divided by the plate in its passage therethrough.

The portion (Fig. 4) of the exhaust fitting is preferably triangular and has a concave forward push closely tted about the rear of the shaft housing 25 to serve as a fairing for the shaft housing and thus reduce the resistance thereof when the shaft housing moves through the water. The top of the fairing portion 35 of the exhaust tting is closed to receive communication with a conventional exhaust manifold 39.

It has heretofore been thought desirable to extend the. lower unit above the anti-cavitation plate in order that its unbroken wall surfaces may constitute stream-lining around the exhaust passage and water pipe or pipes. In the present design this expense is rendered unnecessary by the contour of the exhaust fitting and the relation of the exhaust fitting and the water pipe dii to the tubular shaft housing 25. ./-is shown in Fig. 4, the assembly of these three devices constitutes a very effective stream-lining at greatly reduced cost and weight.

In the construction shown in Figs. 5, 6, and 1, the lower unit 55 is stream-lined in its horizontal cross section to its top surface 56 which is well above the water line. It is connected to shaft housing 51 by an attaching flange 58 on the shaft housing which is bolted to the lower unit. The lower unit has a water inlet passage at 59 in its bow margin which leads centrally to a centrifugal pump runner 60 having a water delivery pipe 5I.

Below the water line the lower unit 55 has oppositely disposed parallel channels 63 formed in its sides. An anti-cavitation plate 64 is slotted at 65 to receive the intervening portion of the The gear casing propery lower unit. The rear of the lower unit is cut away in the vicinity of the water linel to provide a recess at 8B to which the under-water exhaust fitting 61 is complementary, the latter being formed to continue and extend the stream-lining of the lower unit 55. The conventional exhaust manifold 68 leads to this fitting and discharges rearwardly through a flat mouth 6.9 in an anticavitation plate section 10 which is detachably connected with the anti-cavitation plate 64 by means of bolts 1I.

The fact that the bifurcated end of the anticavitation plate 6l opens rearwardly ensures that there will be no crevice into which weeds could be wedged during the forward movement of the device through the water.

In the construction shown in Figs. 8 to 10 the lower unit 15 is stream-lined in its horizontal cross section to a point well above the water 1eve1 and attached to the shaft housing 51 by 2o flange 58 similar to that described in connection with Figs. 5, 6, and '1. The water supply connections may also be similar, these parts being immaterial to the present discussion.

As'in the device shown in Figs. 5, 6, and 7, the housing has parallel grooves 63 in opposite side portions into which the component parts 'i5 and 11 of an anti-cavitation plate assembly are receivable. Each of the anti-cavitation plate elements is bifurcated, one being formed to engage the bow of the lower unit 15 and the other its stern. The plate elements may overlap at It in a transverse horizontal plane and may be held together by screws 19 countersunk in plate element 11.

It will be noted throughout the series of devices herein disclosed, that in each instance the lower unit has a characteristic horizontal fluting which results in the provision of channels 80 and horizontal ribs 8I. Outboard motors are frequently applied to very light craft which have not sufficient weight to offer any appreciable resistance either to the vibrationof the engine or to the bobbing about which results from the movement of the boat rapidly from wave to wave.

By fiuting, corrugating, ribbing, or channeling the exterior wall surfaces of the lower units herein disclosed, the lower unit becomes interlocked or interengaged with the body of water through which the device is passing at any given moment. At high speeds the water has a resistance to displacement which is so great as to amount almost to that which would be offered by a solid body. Hence the motor is, by means of this irnprovement, anchored against vibration and against the skipping motion which has been found so objectionable in the past.

It is noteworthy that this improvement is effected without any increase in water resistance. All of the ribbing is horizontal, and its interaction with the water is 'such that it tends to remain so and hence tends to restore equilibrium to the boat if the bow is elevated or depressed abnormally. In all horizontal cross sections the lower unit may be stream-lined as heretofore, and it is so illustrated.

Not only is this result accomplished without any increase in water resistance, but it is accomplished with a decrease of weight. The corrugations, flutings or ribs and channels provide a sufficient reinforced or bracing effect so that the walls of the lower unit may be decreased in thickness in the channels more than enough to compensate for the increase in the ribs, thus reducing the overall weight of the lower unit.

While the invention has been describedV with particular reference to an outboard motor lower unit, it will be understood that it has application to all outboard driving structures whether or not the engine is such that the device ma'y properly be characterized as an outboard motor.

I claim:

l. As a new article of manufacture, a marine propulsion unit provided below the Water line with outer wall surfaces horizontally uted.

2. As a new article of manufacture, a marine propulsion lower unit stream-lined in its horizontal contours and provided about its streamlined wall surfaces with a series of alternating ribs and intervening depressions comprising a horizontal utng'adapted to interlock the unit with the water through which it is passing.

3. In a. marine propulsion device, the combination with a shaft housing provided at its lower end with a flange comprising an anti-cavitation plate and having a forwardly opening water intake passage leading to a point adjacent the center of said shaft housing, a shaft in said housing, a pump runner on said shaft arranged to receive water from said passage, and an outlet pipe leading upwardly from said pump.

4. In a marine propulsion unit, the combination with an anti-cavitation plate having a rearwardly and vertically opening notch in its rear end, of an exhaust discharge fitting complementary to said notch and provided with a rearwardly directed laterally elongated mouth substantially in the plane of said plate. y

5. In a marine propulsion device, the combination with a lower unit, of a bifurcated anticavitation plate extending about opposite sides of said unit and connected across a margin thereof, and means for securing said plate to said unit.

6. In a marine propulsion clevice,l the combination with a lower unit having laterally opposite channels in its side walls, of an anticavitation plate including vportions engaged in said channels.

7. In a 'marine propulsion device, the combination with a lower unit, of a bifurcated anticavitation plate engaged about the front margin cf said unit and extending rearwardly along the sides thereof, and an exhaust fitting engaging the rear of said unit and connected with said plate to maintain it in clamping engagement with the unit.

9. In a device of the character described, the combination with a lower unit, of an anti-cavitation plate mounted upon said unit and disposed wholly forwardly of the stern margin of said unit.

l0. In a marine propulsion device,.the combination with a lower unit, of a pair of bifurcated anti-cavitation plate elements respectively engaged about the bow and stern margins of the lower unit and connected with each other.

11. In a marine propulsion device, the combination with a lower unit, of a bifurcated anticavitation plate engaged about the front margin of said lower unit and extending along the sides thereof, and means engaged with the rear margin of said unit and connectedwith said plate to hold said plate detachably to said unit.

l2. In a device of the character described, the combination with a marine propulsion lower unit having substantially streamlined contours to a point adjacent its top but below normal water level and there provided atl its stern with a notch opening rearwardly and upwardly, of a waste discharge fitting detachably connected with said lower unit at said notch and adapted to extend in a streamlined form the side contours of said unit. said tting having a rearwardly directed discharge mouth and an upwardly extending pipe connection communicating therewith through said fitting, whereby waste may be discharged below the vwater line without entering said lower unit.

FINN T. IRGENS. 

